Reassessing Tuberculosis Treatment Outcomes by Sputum Liquid Culture Testing at the End of Treatment in Karnataka,...

Tuberculosis (TB) remains a major global health condition, particularly in low- and middle-income countries. Treatment failure and relapse are of great concern, and treatment monitoring is largely dependent on smear microscopy. Smear microscopy has its limitations, particularly in identifying low bacillary loads and viable bacilli. This study aimed to estimate the prevalence of treatment failure and its associated risk factors among drug-sensitive TB (DSTB) patients using sputum liquid culture testing at the end of treatment.

A cross-sectional study was conducted among microbiologically confirmed pulmonary DSTB patients between April and June 2024 in six randomly selected districts of Karnataka, India. Sputum samples obtained at the time of completion of treatment were cultured using the Mycobacterium Growth Indicator Tube (MGIT) liquid culture system in three culture and drug susceptibility testing (C-DST) laboratories in the state. Demographic and clinical information were accessed through Ni-kshay, the case-based web-based TB reporting system used in India. Statistical analysis was performed using Jamovi v2.3 (Jamovi Project, Sydney, Australia).

Among 511 patients enrolled, the mean age was 46 ± 17 years, 70.3% were male, 15.3% had a history of TB, 5.5% were HIV reactive, and 20.7% had diabetes. The mean BMI was 18.9 ± 2.8 kg/m². Liquid culture testing found 40 (7.8%; 95% CI: 5.6%-10.5%) patients to be culture positive. Thus, the TB treatment failure rate was 7.8%. Males and patients with a history of TB had relatively increased risks of treatment failure (RR: 1.27 and 1.18, respectively), but these were not statistically significant. Age, BMI, HIV reactivity, and diabetes also did not demonstrate significant associations with treatment failure.

This study highlights the inadequacy of smear microscopy for treatment outcome measurement and shows that end-of-treatment liquid culture significantly enhances the detection of treatment failure. Scaling up the application of high-sensitivity tests, such as liquid culture, at the programmatic level could enhance outcome classification, enable timely clinical interventions, and reduce recurrence and transmission rates. Programmatic investment in sensitive diagnostic technology for diagnosis and treatment monitoring is essential in the strategy toward India's TB elimination goal.